If you're training for an event we want you to be able to track your effort. Whether you're doing it manually or if you've connected your supporter page with MapMyFitness or Strava, you'll start seeing your total effort in your page:
You can also change display unit to your own preference. Selectable units at user level are km, miles. This will determine the unit synced fitness activities (Strava and Map My Fitness) and aggregate totals are displayed. Don't forget that when you add fitness activity manually you can choose the unit that best describes your activity - this will always override your user specific settings on your page.